JPH07213870A - Electrodialytic treatment - Google Patents

Abstract

PURPOSE: To decrease an organic and an inorganic halogen contents in an aqueous solution by subjecting the aqueous solution of a nitrogen-containing epihalohydrin-based resin to an electrodialysis treatment. CONSTITUTION: The aqueous solution of a nitrogen-containing epihalohydrin- based resin is passed into a second section 4 of an electrodialysis unit cell 2, a sodium hydroxide solution is passed into a first section 3, and sodium chloride or sodium sulfate is passed into an anode section 7. Hydroxide ions existing in the first section 3 are moved into the second section 4 through a first anion selective membrane 5 by generating electric voltage difference, and an organic halogen and an inorganic halogen existing in the resin are moved into the anode section 7 through a second anion selective membrane 6. As the result of electrodialysis treatment, the aqueous solution of nitrogen- containing epihalohydrin-based resin containing a lowered content of the organic halogen and the inorganic halogen is extracted from the second section 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the content of organic and inorganic halogens in an aqueous solution of a nitrogen-containing epihalohydrin resin and the use of the product obtained by the method. More particularly, the present invention relates to subjecting an aqueous solution of a nitrogen-containing epihalohydrin-based resin to an electrodialysis treatment to produce an aqueous solution of a nitrogen-containing epihalohydrin-based resin having a reduced content of organic and inorganic halogens. The aqueous solution obtained by that method is used as an additive in the manufacture of paper.

[0002]

BACKGROUND OF THE INVENTION In recent years, attempts to reduce the use of halogen-containing compounds have gained increased interest, especially in the field of pulp and paper manufacturing. Organic halogens in organic compounds are responsible for the increased halogen loading not only in wastewater but also in paper and paperboard. The epihalohydrin-based resin is, for example, a halogen-containing organic compound that is widely used as an additive in the production of paper as a wet strength enhancer. Many methods have been developed to reduce the organohalogen content of epihalohydrin-based resins. European Patent Application No. 0512423 and U.S. Patent No. 4,857,
Nos. 586 and 4,975,499 relate to treatment of an aqueous solution of an epihalohydrin resin with a strong base. European Patent Application No. 0510987 discloses enzymatic dehalogenation of halogen-containing compounds present in an aqueous solution of an epihalohydrin-based resin. However, a significant drawback of these methods is that they only reduce the organic halogen content, but increase the inorganic halogen content in the form of halogen ions, which keeps the total halogen content in the aqueous solution constant. . This is a serious limitation. What is more, the reaction of organic halogens with halogen ions and organic compounds present in aqueous solution, especially when the pH of the product is reduced to less than 7, especially 3 to 5 to improve storage stability. This is because it is generated by

WO 92/22601 reveals the possibility of removing both organic and inorganic halogens from epihalohydrin resins by passing an aqueous solution of epihalohydrin resin through a strongly basic ion exchange resin. ing. The disadvantage of this method is the discontinuous operation due to the need to regenerate the ion exchange resin from time to time. Also, rinsing and regeneration or backwashing of the resin produces effluents, which still contain organic compounds, causing problems in the wastewater due to their chemical oxygen demand and their rather high salt loading. This is because the chemical for regeneration needs to be used in excess.

The use of electrodialysis has been well documented in the literature. For example, RWBaker et al., Membrane Separations Sys
See tems, Noyes Data Corp., 1991. Electrodialysis is a well established technique for desalination of salty water for the production of portable water and table salt, which is most often used in methods involving inorganic materials. However, according to US Pat. Nos. 4,802,965 and 5,145,569, electrodialysis can also be used to remove salts from aqueous solutions of organic compounds.

[0005]

Therefore, it is an object of the present invention to provide a nitrogen-containing epihalohydrin-based resin for producing an aqueous solution of the nitrogen-containing epihalohydrin-based resin having a reduced content of organic halogen and inorganic halogen. It is to provide a method for treating an aqueous solution. Furthermore, it is an object of the invention to provide a method as described above which can be carried out continuously. Another object of the present invention is to provide the above method for producing an aqueous solution having a reduced content of halogenated products and halogenated by-products. Yet another object of the present invention is to provide the above method for reducing the content of organic halogen and inorganic halogen in an aqueous solution of an organic compound containing halogen to a level lower than that obtained by applying the known method. It is to be.

[0006]

The objects of the invention are achieved by the method as further specified in the claims. More specifically, the present invention relates to a method for reducing the content of organic halogen and inorganic halogen in an aqueous solution of an epihalohydrin-based resin containing nitrogen by electrodialysis.

According to the present invention, it has been found that it is possible to subject an aqueous solution of an epihalohydrin-based resin containing nitrogen to electrodialysis without clogging the membrane. Further, the electrodialysis treatment of the aqueous solution containing the epihalohydrin-based resin containing nitrogen not only removes the halogen ions bound to the ion, but also substantially reduces the content of the organic halogen covalently bound to the organic compound present in the solution. It was unexpectedly discovered to reduce to. It is believed that epoxide groups are created in the epihalohydrin-based resin when the organic bound halogen is removed, and that the organic bound halogen is converted to an inorganic halogen.

Electrodialysis means any electrochemical process involving at least one ion selective membrane. Organic halogen means all halogens attached to an organic molecule. These halogens are preferably bound to the organic compound by covalent bonds. Inorganic halogen means halogen in the form of halogen ions, preferably halide ions such as Cl ⁻ and Br ⁻ . Total halogen content is the sum of organic and inorganic halogens.

According to the method of the present invention, any type of nitrogen-containing epihalohydrin resin can be used. Suitably, the resins are produced by reacting a nitrogen-containing precursor selected from amines, polyamines, polyaminoamides and mixtures thereof with epihalohydrin, for example these resins are described by Dan Eklund and Tom Lindstrom in "Paper Chemistry". , Introduction ", page 97, DT Paper Science Publications, 1
991. The resins are preferably polyaminoamide-epihalohydrin-based resins, which are also referred to as polyamidoamine-epihalohydrin-based resins. Epihalohydrins that can be used include epibromohydrin and epichlorohydrin, with epichlorohydrin being preferred. Preferably, the resin is produced using 0.5 to 2.0 moles of epihalohydrin per mole of basic nitrogen in the nitrogen-containing precursor.

The nitrogen-containing precursor is preferably the polyaminoamide reaction product of a polycarboxylic acid, preferably a dicarboxylic acid, and a polyamine. The term "carboxylic acid" is meant to include carboxylic acid derivatives such as anhydrides, esters and half esters. Suitable polycarboxylic acids include saturated or unsaturated aliphatic or aromatic dicarboxylic acids. The polycarboxylic acid preferably contains less than 10 carbon atoms.

Preferred polycarboxylic acids include oxalic acid,
Examples thereof include malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and derivatives thereof.
Also, mixtures of these compounds may be applied. Adipic acid is preferred.

Suitable polyamines have the formula:

[0013]

[Chemical 1] (In the formula, R ^{1 to} R ⁵ are hydrogen or lower alkyl, preferably
A lower alkyl up to C ₃ and a to d represent an integer of 0 to 4), or a mixture thereof. Preferred polyalkylene polyamines include diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, dipropylene triamine, and mixtures thereof.

The polyamines of formula (I) may be combined with other polyamines or mixtures of other amines. These amines have the following formulas II-VII:

[0015]

[Chemical 2] (In the formula, R ^{6 to} R ¹⁴ represent hydrogen or lower alkyl, preferably lower alkyl up to C ₃ , e to 1 represent an integer of 0 to 4, and m represents an integer of 0 to 5.) Have.

The polycarboxylic acid and the polyamine are 1: 0.5-
It can be applied in a molar ratio of 1: 1.5.

The nitrogen containing epihalohydrin resins of the present invention are present in an aqueous solution which may contain a water miscible solvent such as methanol, ethanol or dimethylformamide. The aqueous resin solution is preferably prepared from an aqueous solution of a precursor containing nitrogen. The reaction of epihalohydrin with a nitrogen-containing precursor is described in many different ways known to those skilled in the art, for example in WO 92/22601, which is hereby incorporated by reference. Can be done in different ways. The molecular weight of the resin is not important.
The molecular weight of the resin is in the range of 50,000 to 1,000,000, or higher.

The production of epihalohydrin-based resins results in the formation of halogenated by-products. Aqueous resin solutions produced by the reaction of amines, polyamines or polyaminoamides with epihalohydrins have undesired by-products, for example:
Includes 1,3-dihalo-2-propanol (DXP) and 3-halo-1,2-propanediol (XPD). In particular, 1,3-dichloro-2-propanol (DCP) and 3-chloro-1,2-propanediol (CPD) are produced when epichlorohydrin is used. Reducing the content of organic halogens in such low molecular weight organic compounds as well as in organic compounds containing oligomeric halogens present in the resin solution is encompassed by the method of the present invention. The electrodialysis treatment of the present invention can convert DXP and XPD and residual epihalohydrin to the halogen-free compound glycidol and finally to glycerol.

The solid content of the aqueous solution to be subjected to the electrodialysis treatment may be as high as 30% by weight or more, preferably 5 to 25% by weight, most preferably about 15 to 20% by weight. The viscosity of the aqueous solution is preferably in the range of 1-100 mPas, most preferably 5-60 mPas. After electrodialysis treatment, the viscosity of the aqueous solution may be increased, for example, by further polymerization of the resin in a known manner before its use as a wet strength enhancer.

Electrodialysis methods and devices are known to those skilled in the art, and electrodialysis devices are described, for example, by RWBaker et al. In "Membrane Separation System", Noyes Data Cor.
p.), 1991 and manufactured from conventional parts.

In the method of the present invention, the electrodialysis treatment can be carried out in an electrodialysis machine which comprises at least one electrodialysis unit cell arranged between the anode and the cathode, the side of which the unit cell faces the anode. In the anion-selective membrane bounded by an anion-selective membrane, whereby an aqueous solution of an epihalohydrin-based resin containing nitrogen is supplied to the compartment and halogen ions are generated by creating a potential difference between the anode and the cathode. Move through anion selective membrane. The compartment to which the aqueous resin solution is fed is, on the side facing the cathode, bounded by said membrane, preferably by an anion-selective membrane, a cation-selective membrane or a bipolar membrane, either membrane blocking the transport of the nitrogen-containing epihalohydrin-based resin. Is determined.

The halogen-free anion is supplied by supplying a nitrogen-containing aqueous solution of the epihalohydrin-based resin through a membrane facing the cathode, or is appropriately introduced into a compartment contained in the aqueous resin solution. Suitable halogen-free anions include hydroxides, sulfates, phosphates, acetates, formates and mixtures thereof, preferably hydroxides. In that process, the counterion is not critical, unless an aqueous solution of a halogen-free anion salt is suitably used and the electrodialysis process and equipment are not adversely affected. Halogen-free anion salts should have sufficient solubility in the aqueous solution used to carry out the electrodialysis treatment, are made from their metal salts, preferably alkali metal salts are suitably used. Examples of suitable metal salts of halogen-free anions include LiOH, NaOH, KOH, Na ₃ PO ₄ ,
Examples include Na acetate and Na formate. NaOH and KOH are preferably used. The aqueous solution used should be from 0.001 M or less to the saturation concentration of the aqueous solution used, preferably 0.05-10 M.
Most preferably, it has a halogen-free anion salt concentration of 0.1-5 M.

In a preferred embodiment of the invention, the electrodialysis unit cell comprises first and second compartments and first and second anion selective membranes. The first anion selective membrane faces the cathode, the second anion selective membrane faces the anode, the first compartment faces the cathode, and is bounded by the first anion selective membrane, and The second compartment is bounded by the first and second anion selective membranes. In the method, an aqueous solution of an epihalohydrin-based resin containing nitrogen is supplied to the second compartment, an anion containing no halogen is supplied to the first compartment, is moved in the first anion selective membrane, and halogen ions are second It can be moved through the anion selective membrane. There may be an anode compartment adjacent to the unit cell and facing the anode.

According to a further preferred embodiment of the present invention,
An electrodialysis unit cell comprising first and second compartments and first and second anion selective membranes further comprises a third compartment and a cation selective or bipolar membrane facing the anode. In the method, halogen ions are transported in a third compartment bounded by a second anion-selective membrane and a cation-selective or bipolar membrane. The feedstock for the third compartment is
If the membrane of the third compartment facing the anode is a cation selective membrane, it is suitable that it is an aqueous solution of a salt or metal halide, and if the membrane of the third compartment facing the anode is a bipolar membrane, Suitably it is water or an aqueous hydrochloric acid solution. There may be an anode compartment adjacent to the unit cell and facing the anode.

In another preferred embodiment of the invention, the electrodialysis unit cell comprises a first and a second compartment, an anion-selective membrane and a bipolar membrane, the bipolar membrane facing the cathode and being anion-selective. The membrane faces the anode, the first compartment faces the cathode and is bounded by a bipolar membrane, and the second compartment is bounded by a bipolar membrane and an anion selective membrane. There is. In the method, an aqueous solution of an epihalohydrin-based resin containing nitrogen is supplied to the second compartment, an aqueous solution of acid or salt is supplied to the first compartment, and halogen ions are moved through the anion selective membrane. Also, water may be supplied to the first compartment. There may be an anode compartment adjacent to the unit cell and facing the anode.

In another preferred embodiment of the invention, an electrodialysis unit cell comprising a first and a second compartment, an anion selective membrane and a bipolar membrane facing the cathode comprises a cation selective membrane facing the third compartment and the anode. Further includes a membrane.
In this method, halogen ions are transported in a third compartment bounded by an anion selective membrane and a cation selective membrane. The feedstock to the third compartment may be an aqueous solution of salt, metal halide or acid. There may be an anode compartment adjacent to the unit cell and facing the anode.

The aqueous solutions of salts, metal halides and acids that can be used in the process of the present invention are not critical, so long as the electrodialysis process and equipment are not adversely affected by these solutions. Suitable salts include salts having good conductivity, for example salts of strong bases and strong acids, for example NaCl, KCl, LiCl, Na ₂ SO ₄ ,
K ₂ SO ₄ , Li ₂ SO ₄ , NaNO ₃ , NH ₄ Cl and Rq NCl. The salt is preferably electrochemically inert. The salt concentration in the aqueous solution used may be from 0.001 M to saturation of the solution, preferably 0.1-5 M. Examples of suitable metal halides include alkali metal halides,
For example, LiCl, LiBr, NaCl, NaBr, KCl, and KBr. NaCl and KCl are preferably used. The metal halide concentration in the aqueous solution used may be from 0.001 M up to the saturation concentration of the solution, preferably 0.1-5.0 M. Suitable acids include organic and inorganic acids and mixtures thereof, preferably inorganic acids. Examples of suitable inorganic acids include hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid,
Hydrochloric acid and sulfuric acid are preferably used. The acid concentration of the aqueous solution used is from 0.001 M to 10 M or more, preferably 0.1-
5 M is enough.

According to another preferred embodiment of the present invention, the nitrogen-containing aqueous solution of the epihalohydrin-based resin is pretreated with hydroxide ions before the electrodialysis treatment, whereby a part of the organic halogen in the resin is removed. It may be replaced by hydroxide and the electrodialysis treatment described below may be carried out in commercially available equipment for desalination of water. It was surprisingly found that this pretreatment did not result in the undue polymerization of the resin in solution or on the membrane. The pretreatment can be performed by adding a salt containing hydroxide or an aqueous solution thereof to the resin solution. Mixtures of metal hydroxides or metal hydroxides, preferably alkali metal hydroxides, are suitably used. Examples of suitable metal hydroxides include LiOH, NaOH and KOH. NaOH and KOH are preferably used. Of resin solution after pretreatment
The pH is suitably 5 or more, preferably 8 to 13.

According to another preferred embodiment of the invention involving hydroxide pretreatment of the resin solution, the electrodialysis unit cell comprises a first and a second compartment, an anion selective membrane and a first cation selective membrane. You can The anion selective membrane faces the anode, the first cation selective membrane faces the cathode, the first compartment faces the cathode, and is bounded by the first cation selective membrane, and the second The compartment is bounded by a first cation selective membrane and an anion selective membrane. In the method, a nitrogen-containing epihalohydrin-based resin and, for example, an aqueous solution of hydroxide ion in the form of a salt containing hydroxide are supplied to the second compartment, and halogen ions are moved through the anion-selective membrane. The hydroxide ion counterions are transferred through the first cation selective membrane to the first compartment. Adjacent to the unit cell, facing the anode, there may be an anode compartment through which an aqueous solution of the metal halide or acid may pass. Water or preferably an aqueous solution of metal hydroxide or metal halide is fed to the first compartment.

According to another preferred embodiment of the invention involving pretreatment of the resin solution, the electrodialysis unit cell comprising the first and second compartments, an anion selective membrane and a first cation selective membrane comprises a third compartment and It further comprises a second cation selective membrane facing the anode, whereby halogen ions are transported in a third compartment bounded by the anion selective membrane and the second cation selective membrane. An aqueous solution of said salt or metal halide can be fed to the third compartment and an aqueous metal hydroxide solution can be fed to the first compartment. Adjacent to the unit cell, facing the anode, there may be an anode compartment,
An aqueous metal hydroxide solution can pass through it.

The anion-selective membranes used according to the invention (also called anion-exchange membranes) allow the exchange of anions between the compartments bounded by such anion-selective membranes. An example of a suitable anion selective membrane is an anion selective membrane (produced by Tokuyama Soda) sold under the trade name Neoceptor. Cation selective membranes (also called cation exchange membranes) allow the exchange of cations between the compartments bounded by such cation selective membranes. An example of a cation selective membrane suitable for use in the method of the invention is the cation selective membrane sold under the trade name Nafion (manufactured by DuPont). Bipolar membranes allow the electrically forced dissociation of water, and suitable bipolar membranes include those produced and sold by WSI. The compartment in the electrodialysis device defined by the gap between the membrane and the gap between the membrane and the electrode comprises an inlet and an outlet for the flow of the solution.

The current density in the method of the present invention is 0.01-5 k
It is preferably within the range of A / m ² , and most preferably within the range of 0.1-1 kA / m ² .

The temperature of the aqueous solution supplied to the compartment should be compatible with the membrane and the resin solution used. If the temperature is too high, chemical reactions, such as polymerization, may occur, so it is preferred that the temperature be low to avoid undue polymerization of the epihalohydrin-based resin. The solution is preferably cooled in order to balance the temperature rise due to the electrodialysis treatment. The temperature may range from the freezing point of the aqueous solution to about 40 ° C, preferably 20 ° C or lower, most preferably 5-20 ° C.

According to a preferred embodiment of the present invention nitrogen
Aqueous solution of epihalohydrin resin containing
Contacted with exchange resin, which was
Simultaneously or thereafter, preferably simultaneously with electrodialysis treatment
Can then be done. Appropriately, the simultaneous mode of operation is applied.
The anion exchange,
Contains resin. Anion exchange resins are known to those skilled in the art.
Ullmann's Encyclopedia of Industrial Chemistr
Reference is made to y, Volume A14, page 393ff, 1989. Appropriately
Generally a cationic group such as R^-NH ₃ ⁺, R₂NH₂ ⁺ , R₃N
H⁺ , R_FourN⁺ And R_FourS⁺ (Less in each of the listed groups
And one R represents a polymer matrix)
A basic anion exchange resin is used. Poly available
Examples of marmatrix include polystyrene resin, poly
Acrylic resin, phenol-formaldehyde resin, and
And matrix based on polyalkylamine resin
Is mentioned. Anion exchange that can be used in the method of the invention
The resin was described by Ullmann in the above edition,
International Publication No. 92/22601, which
Included herein as reference.

The basic anion exchange resin used in the method of the present invention preferably contains a tertiary amino group or a quaternary ammonium group or a mixture thereof. Strongly basic anion exchange resins are preferred over weakly basic anion exchange resins. Examples of strongly basic anion exchange resins include resins having a quaternary ammonium group with three lower alkyl substituents or a quaternary ammonium group with at least one lower alcohol substituent. Also, mixed resins may be used. The most preferred anion exchange resin is a strongly basic anion exchange resin of the type having a quaternary ammonium substituent selected from the group consisting of trimethylammonium, dimethylethanolammonium, and mixtures thereof.

The aqueous solution of the nitrogen-containing epihalohydrin-based resin may have a low pH, such as a pH of about 4 or less, before it is subjected to the electrodialysis treatment. During that process,
The pH is often raised to high values, for example pH above about 12. Suitably, the pH of the aqueous resin solution is acid adjusted after treatment to give a product having a pH below 5. pH is about 3-5
It is preferable to adjust the value of to obtain an aqueous resin solution having better stability after storage. The pH may be adjusted by using organic or inorganic acids or mixtures thereof as appropriate. Preferred organic acids include formic acid, acetic acid and citric acid, while preferred inorganic acids include sulfuric acid and phosphoric acid.

In another preferred embodiment of the invention,
The polarities of the electrodes are switched at least once during the process, suitably at regular intervals. Preferably, this can be applied in order to minimize fouling of the membrane delimiting the compartment to which the aqueous resin solution is fed when unit cells are used that do not contain a bipolar membrane. Suitably, the feedstock to the compartment adjacent to the compartment to which the aqueous resin solution is supplied is also switched at least once, preferably at the same intervals as the polarity of the electrodes, so as to avoid introducing halogen ions into the aqueous resin solution. If desired, additional feedstock may be switched, as will be readily appreciated by those skilled in the art.

According to another preferred embodiment of the invention,
The electrodialysis machine includes at least two electrodialysis unit cells. Suitably, the device comprises a row of adjacent unit cells arranged in the form of a stack between the anode and the cathode. The multi-unit cell device may include unit cells of the same type or unit cells of different types. It will be understood by those skilled in the art which unit cells are preferably stacked. In a multi-unit cell device, the discharge stream from one cell compartment may be the feed stream of another cell compartment.

In the method of the present invention, the anode can be made of a conductive material that is stable under anodic polarization in the anolyte. Dimensionally stable anodes having an active surface layer of ruthenium, iridium, platinum, palladium or mixtures thereof, which can be made of titanium, zirconium, hafnium, niobium or mixtures thereof, can be used. Examples of suitable commercial anodes are:
It is an anode sold by Permuskand under the trade name DSA. Also, a suitable anode can be made of graphite.

Typically, the anodic reaction is oxygen evolution by the following reaction.

H₂O → 1 / 2O₂ + 2H⁺ + 2e^-  If halogen ions are present in the anolyte, the halogen
Carbon production will occur at the anode. Thus, chlorine
If on is present in the anolyte, chlorine formation will
It is caused by the reaction.

2Cl ⁻ → Cl ₂ + 2e ⁻ Alternatively, the anode may be a hydrogen-polarized anode, in which case hydrogen gas is oxidized in the gas diffusion electrode by the following reaction.

H ₂→ 2H⁺ + 2e^- Stable conductivity in the catholyte under cathodic polarization
It is preferred that it is made of a conductive material. Cathode material
Examples of steel, stainless steel, nickel and grapher
Ito. Also, the cathode can be made of various catalysts, eg
For example, it can be coated with ruthenium oxide. Typically,
The sword reaction is hydrogen generation by the following reaction.

2e ⁻ + 2H ₂ O → H ₂ + 2OH ⁻ Alternatively, the cathode may be an oxygen polarized cathode, in which case oxygen is reduced in the gas diffusion electrode by the following reaction.

1 / 2O ₂ + H ₂ O + 2e ⁻ → 2OH ⁻ The electrodialysis treatment of the present invention can be carried out as a batch method, a semi-continuous method or a continuous method. Semi-continuous or continuous methods are preferably used, most preferably continuous methods. A continuous process involves continuously feeding an aqueous solution of an epihalohydrin-based resin containing nitrogen into a cell compartment, continuously subjecting the resin solution to an electrodialysis treatment, and then continuously withdrawing the solution from that compartment. The resin solution can be circulated, and it is appropriately circulated until the desired content of organic and inorganic halogens is obtained.

The flow rates which can be carried out according to the invention depend on the process conditions and are easily determined by the person skilled in the art in view of such factors as the electrodialysis device used, the size of the compartment, the production capacity and the current density. .

The present invention also provides an aqueous solution of a nitrogen-containing epihalohydrin-based resin having a reduced content of organic and inorganic halogens obtained by the process of the invention as an additive in the manufacture of paper, cardboard and paperboard. Regarding the use of. This aqueous resin solution is preferably used as a wet strength enhancer, but it may also be used as a retention aid, anionic debris scavenger and sizing promoter.

The present invention will be described in more detail with reference to the accompanying drawings 1-5. However, the invention is not limited to the described embodiments, but many other variants are feasible within the scope of the claims. The solutions below are aqueous solutions.

FIG. 1 illustrates an electrodialysis machine 1 including one electrodialysis unit cell 2 arranged between an anode A and a cathode C. This unit cell comprises first and second compartments 3, 4 and first and second anion selective membranes 5, 6
including. Yet another section adjacent to this unit cell (hereinafter referred to as anode section 7) faces the anode. An aqueous solution of the epihalohydrin-based resin containing nitrogen is passed through the second compartment 4, a sodium hydroxide solution is passed through the first compartment 3 and a solution of sodium chloride or sodium sulfate is passed through the anode compartment 7.

By creating a potential difference between the electrodes,
The hydroxide ions present in the first section 3 are moved to the second section 4 through the first anion selective membrane 5, and the organic halogen and the inorganic halogen present in the resin are passed through the second anion selective membrane 6 as halogen ions. It is moved to the anode compartment 7. As a result of the electrodialysis treatment, an aqueous solution of epihalohydrin-based resin containing nitrogen with a reduced content of organic and inorganic halogens is withdrawn from the second compartment.

The feedstock to the anode compartment in the process of the invention may be an aqueous solution of the salts, metal halides, acids or metal hydroxides mentioned above. These ions have a good conductivity in solution and they are suitably electrochemically inert.

FIG. 2 shows an electrodialysis device 8 similar to the device outlined in FIG. 1, in which the unit cell 9 comprises a third compartment 10 and a cation-selective membrane 11 facing the anode. Yet another compartment adjacent to the electrodialysis unit cell (hereinafter referred to as the anode compartment 12) faces the anode. The solution is passed through the first compartment 3 and the second compartment 4 described above. In addition, sodium chloride solution is passed through the third compartment 10 and sodium hydroxide solution is passed through the anode compartment 12.

By applying a potential difference between the electrodes, the hydroxide ions present in the first compartment 3 are moved in the first anion selective membrane 5 and the halogen ions present in the second compartment 4 are converted to the second ion. Halogens that are displaced in the anion selective membrane 6 and are forced to move sodium ions present in the anode compartment 12 through the cation selective membrane 11 to the third compartment 10, thereby entering the second compartment 4. The ions are combined in the third compartment 10 with halogen ions which form a fortified sodium halide solution. By this electrodialysis treatment, the contents of organic halogen and inorganic halogen are reduced in the resin aqueous solution. The hydroxide feed streams are each divided into a feed solution to the first compartment and a feed solution to the anode compartment, and the effluent solution from said compartments can be combined in one stream which can be circulated.

The electrodialysis device may include more than one unit cell. FIG. 3 shows a device 13 comprising two unit cells of the type outlined in FIG. 2 between anode A and cathode C.
Indicates. The anode compartment 14 is arranged between the anode and the unit cell facing the anode. The solutions are preferably circulated back to the compartment from which they originated, or to the corresponding compartment of another cell.

If a bipolar membrane is used in the method of the present invention, the electrodialysis device may be designed as outlined in FIG. In the device 15, the unit cell 16 is a first compartment 17,
It includes a second compartment 18 and a third compartment 19, a bipolar membrane 20, an anion selective membrane 21 and a cation selective membrane 22. A further compartment adjacent to the electrodialysis unit cell (hereinafter referred to as the anode compartment 23) faces the anode. An aqueous solution containing an epihalohydrin-based resin containing nitrogen is supplied to the second compartment 18, an aqueous sulfuric acid solution is supplied to the anode compartment 23 through the first compartment 17, and a water or hydrochloric acid solution is passed to the third compartment 19.

By creating a potential difference between the electrodes,
The electrically forced dissociation of water in the bipolar membrane 20 results in the transfer of hydroxide ions into the second compartment 18. in addition,
The halogen ions present in the second compartment are moved to the third compartment 19 through the anion selective membrane 21, and the protons supplied to the anode compartment 23 are moved to the third compartment 19 through the cation selective membrane 22. , Where a fortified solution of hydrohalic acid is produced.

Suitably, the bipolar membrane multi-unit cell device comprises at least one, and preferably one or more unit cells of the type comprising anion selective membranes and bipolar membranes. Several such cells are stacked between the electrodes,
And it is preferable that it faces the cathode. The device preferably further comprises a unit cell of the type described in FIG. 4 facing the anode.

FIG. 5 is a schematic diagram showing an electrodialyzer that can be used to reduce the content of organic and inorganic halogens in aqueous resin solutions pretreated with hydroxide ions.
The device 24 comprises two different electrodialysis unit cells,
The first unit cell 25 faces the cathode, and the first section 26 and the second section 27, the first cation selective membrane 28.
In addition, the second unit cell 30 includes an anion selective membrane 29, and the second unit cell 30 includes a first section 31, a second section 32, a third section 33,
It includes a first cation selective membrane 34, an anion selective membrane 35 and a second cation selective membrane 36. A further compartment adjacent to the second electrodialysis unit cell (hereinafter referred to as the anode compartment 37) faces the anode. An aqueous solution containing a nitrogen-containing epihalohydrin-based resin and sodium hydroxide is passed through the second compartments 27 and 32 of both unit cells, and an aqueous sodium hydroxide solution is passed through the first compartment 26 of the first unit cell, and an aqueous sodium chloride solution. Is passed through the first compartment 31 of the second unit cell, the hydrochloric acid aqueous solution is passed through the third compartment 33, and the sulfuric acid aqueous solution is passed through the anode compartment 37.

By applying a potential difference between the electrodes, the halogen ions present in the resin solution pass through the anion selective membranes 29, 35 of both unit cells to the first section 31 and the third section 33 of the second unit cell, respectively. The sodium ions present in the resin solution through the first cation-selective membranes 28, 34 of both unit cells to the respective first compartments 26, 31 of both unit cells. The resin solution can be recycled and additional sodium hydroxide can be added to the resin solution during the process.

A multi-unit cell apparatus for the treatment of an aqueous resin solution pretreated with hydroxide ions as outlined in FIG. 5 comprises at least one, preferably one, of a type comprising a cation selective membrane and an anion selective membrane. It is suitable to include more than one unit cell. It is preferred that some such cells are stacked between the electrodes and face the cathode. The device preferably further comprises a unit cell facing the anode of the type comprising a first cation selective membrane, an anion selective membrane and a second cation selective membrane.

The invention will be further described by the following examples. However, these examples are not intended to limit the scope of the invention. The number of copies and%
Unless otherwise noted, they relate to parts by weight and% by weight, respectively. The solution used in the examples is an aqueous solution.

[0062]

Example 1 A polyaminoamide-epichlorohydride prepared as described in Example 3 of WO 92/22601, using an electrodialysis device of the type substantially outlined in FIG. It was used for electrodialysis treatment of phosphorus resin. The resin solution is 20% by weight
It has a solid content of 12 mPas and a treatment of 20 mPas.
Started at a temperature of ° C.

About 2 liters of a 1 M sodium hydroxide solution and 2 liters of a 0.1 M sodium chloride solution were initially passed through the compartment described in FIG. The method consists of continuously pumping the solution into the compartment at a flow rate of 140 ml / hour,
This was done by passing a current of A through the compartment. Initial voltage is 6.
It was 9V. The electrodialyzer had an electrode surface area of 250 cm ² and thus a current density of 40 mA / cm ² .

After 100 minutes, the treatment was stopped, the recovered resin solution was heated to 35 ° C. and kept at this temperature until a viscosity of 20 mPas (25 ° C.) was reached. The pH of the resin solution was adjusted to 3.5 by adding sulfuric acid.

The analytical data of the resin solution are as follows.

[0066] The total chlorine content was measured using an AOX combustor according to conventional methods. The content of inorganic chlorine was measured by using argentometry. The content of organic chlorine was calculated as the difference between the content of total chlorine and the content of inorganic chlorine. By using a gas chromatographic method with a detection limit of 8 ppm, DCP and
The content of CPD was detected. DI AOX (Absorptive Organic Halogen)
N (German Industrial Standard) 38049, part 14

As is apparent, a considerable reduction in the content of organic and inorganic chlorine and by-products was obtained.

Example 2 In this example, with the difference that the space between the two anion-selective membranes pumping the resin solution is filled with a strongly basic anion exchange resin (Levatit ™ M206, manufactured by Bayer). The electrodialysis device of Example 1 was used.

The epihalohydrin-based resin, NaOH and NaCl solutions initially used in the method of Example 1 were similarly used in this example. This solution was pumped into a compartment with a flow rate of 190 ml / h, during which a current of 10 A was passed between the electrodes. The voltage was about 7.0-8.0V.

After 3 hours, the treatment was stopped, and about 20 mPa
The recovered resin solution was heated to 30 ° C. for further polymerization until a viscosity of s 2 was reached. The pH was then adjusted to 3.6 with sulfuric acid.

The analytical data of the resin solution were as follows.

[0072] Analytical data was measured as described in Example 1.

Example 3 The electrodialysis device of Example 1 was used in this example with the difference that the first anion selective membrane facing the cathode was replaced by a cation selective membrane. A polyaminoamide-epichlorohydrin-based resin was prepared by a method similar to that described in Example 3 of WO 92/22601,
A molar ratio of epichlorohydrin increased by 5% was used. The resin solution had a solids content of 19% by weight, a pH of 5, and a volume of 19 m
It had a viscosity of Pas.

20 ml of 50% NaOH and 85 of water are added to this resin solution.
Sodium hydroxide solution prepared from ml at room temperature
Pretreatment by adding to 395 g. The resulting resin solution had a solids content of 15% by weight. The alkaline pretreated resin solution was placed in a beaker cooled in an ice bath and continuously pumped into the second compartment at a flow rate of 5 l / h. In addition, first a 1 M sodium hydroxide solution was continuously pumped into each of the first and anode compartments, and first a 0.1 M sodium chloride solution was continuously pumped into the third compartment. Initial current and voltage are 10.0 respectively
A and 9.5V.

After 3 hours, 5 ml of 50% NaOH solution was further added to the pretreated resin solution. The method was stopped after 4.25 hours. The alkaline resin solution (pH = 13) was heated to 40 ° C. and kept at this temperature until a viscosity of 20 mPas was reached. pH
Was adjusted to 3.6 with sulfuric acid. The product had a solids content of 17.7% by weight.

The analytical data of the resin solution are as follows.

[0077] Analytical data was measured as described in Example 1.

Example 4 A polyamino-amide-epichlorohydrin-based resin prepared as described in Example 3 for an electrodialysis machine of the type substantially as outlined in FIG. 4 containing a bipolar membrane. Used for electrodialysis of the solution. 395 g of the resin solution was added to 105 ml of water.
Diluted with to give 15 wt% solids. The resin solution was cooled in an ice bath and continuously pumped into the second compartment at a flow rate of 7.5 l / h. In addition, first a 1 M sulfuric acid solution and water were continuously pumped into the compartments described in FIG. In that method, the current density and voltage were 5.0 A and 18-30 V, respectively.

After 1 hour 50 minutes, the electrodialysis treatment was stopped,
The resin solution was heated to 30 ° C. and kept at this temperature until a viscosity of 20 mPas was reached. The pH was adjusted to 3.5 by adding sulfuric acid.
Adjusted to.

The analytical data of the resin solution were as follows.

[0081] Analytical data was measured as described in Example 1.

Example 5 In this example, the wet strength efficiency of the resin solutions prepared in Examples 1-4 was tested. Test sheets of about 70 g / m ² were prepared on a pilot paper machine (speed 2 m / min, capacity 2 kg / h). The finish consisted of a 30/35/35 blend of bleached pine sulphate / Kaba sulphate / beech sulphate which had been broached to a Shopper-Leigler freeness of 26 ° SR. 5% by weight of filler DX 40 (Omma
(Omua)) and clay (kaolin B) were added to the raw materials at a temperature of 25 ° C. The resin solution was supplied to a paper machine after diluting the raw materials. The raw material consistency in the headbox is 0.3% and the pH is 7. for all products and concentrations.
It stayed in the range of 2-7.8 and was not adjusted. The temperature of the cylinder in the drying section was adjusted to 60 ° C / 80 ° C / 90 ° C / 110 ° C.

The paper was tested 2 hours before the test for 30 minutes
Cured at 100 ° C. 5 strips of paper strip in distilled water at 23 ° C
Immersion for a minute, after which the rupture length was measured using an Alwetron TH1 ™ hydrodynamic tester (Gockel & Co. GmbH, Munich).

The test results were as follows. Dose (dry solids wet breaking lengths (m)% and standards) Example 1 Example 2 Example 3 Example 4 0.3 730 730 840 810 0.6 980 990 1120 1140 0.9 1180 1140 1295 1280

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an electrodialysis device including one electrodialysis unit cell containing two anion selective membranes.

FIG. 2 shows the electrodialysis device of FIG. 1 further including one cation selective membrane.

3 is a schematic diagram showing an electrodialysis device including the two electrodialysis unit cells of FIG. 2. FIG.

FIG. 4 is a schematic diagram showing an electrodialysis device including one anion selective membrane, one cation selective membrane and one bipolar membrane.

FIG. 5 is a schematic diagram showing an electrodialysis device including two different electrodialysis unit cells suitably used when the aqueous resin solution is pretreated with hydroxide ions.

[Explanation of symbols]

 1,8,13,15,24-electrodialysis device 2,9,16,30-electrodialysis unit cell 3,17,26,31-first compartment 4,18,27,32-second compartment 5-th One anion selective membrane 6-Second anion selective membrane 7,12,14,23,37-Anode compartment 10,19,33-Third compartment 11,22-Cation selective membrane 20-Dipolar membrane A-Anode C-Cathode

Claims (14)

[Claims] 1. A method for reducing the content of organic and inorganic halogens in an aqueous solution of a nitrogen-containing epihalohydrin resin, the method comprising subjecting the aqueous solution to an electrodialysis treatment. 2. The electrodialysis treatment is carried out in an electrodialysis machine comprising at least one electrodialysis unit cell arranged between an anode and a cathode, the unit cell being provided with an anion selective membrane on the side facing the anode. A bounded compartment is included whereby an aqueous solution of an epihalohydrin-based resin containing nitrogen is supplied to the compartment, and a halogen ion is generated in the anion selective membrane by creating a potential difference between the anode and the cathode. The method of claim 1, wherein the method comprises moving. 3. The electrodialysis unit cell 2 comprises a first section 3 and a second section 4 and a first anion selective membrane 5 and a second anion selective membrane 6, the first anion selective membrane 5 facing the cathode C. The first compartment 3 faces the cathode and is bounded by the first anion selective membrane 5 and the second compartment 4 is bounded by the first anion selective membrane 5 and the second anion selective membrane 6. Whereby an aqueous solution of the epihalohydrin-based resin containing nitrogen is supplied to the second section 4, a halogen-free anion is supplied to the first section 3, and a halogen ion is supplied to the second anion selective membrane 6 The method according to claim 2, wherein the method comprises moving the inside. 4. The electrodialysis unit cell 9 is a third compartment.
10 further comprising a cation selective membrane 11 facing the anode A, whereby halogen ions are transferred into the third compartment 10 bounded by the second anion selective membrane 6 and the cation selective membrane 11. The method according to claim 3, wherein 5. The electrodialysis unit cell further comprises a third compartment and a bipolar membrane facing the anode, whereby
4. The method of claim 3, wherein the halogen ions are transferred into a third compartment bounded by a second anion selective membrane and a bipolar membrane. 6. The electrodialysis unit cell comprises a first compartment and a second compartment, an anion selective membrane and a bipolar membrane, the bipolar membrane facing the cathode and the first compartment facing the cathode. And a second compartment is bounded by a bipolar membrane and a second compartment is bounded by a bipolar membrane and an anion-selective membrane, whereby an aqueous solution of the epihalohydrin-based resin containing nitrogen is contained in the second compartment. The method according to claim 2, characterized in that an acid or salt aqueous solution is supplied to the first compartment, and halogen ions are moved in the anion selective membrane. 7. The electrodialysis unit cell 16 is a third compartment.
A third compartment 19 further comprising 19 and a cation selective membrane 22 facing the anode A, whereby halogen ions are bounded by the anion selective membrane 21 and the cation selective membrane 22.
7. The method according to claim 6, characterized in that it is moved in. 8. The electrodialysis unit cell 25 is a first compartment.
26 and a second compartment 27, an anion selective membrane 29 and a first cation selective membrane 28, the first cation selective membrane 28 facing the cathode C, the first compartment 26 facing the cathode, And the second compartment 27 is bounded by the first cation selective membrane 28 and the anion selective membrane 29, whereby the epihalohydrin-based resin containing nitrogen and water are bound. A method according to claim 2, characterized in that an aqueous solution of oxide ions is fed to the second compartment 27 and the halogen ions are moved through the anion selective membrane 29. 9. The electrodialysis unit cell 30 is a third compartment.
33 and a second cation selective membrane 36 facing the anode A, whereby halogen ions are anion selective membrane 35.
And a second cation selective membrane 36 to move into a third compartment 33 bounded by the second cation selective membrane 36. 10. The method according to claim 1, wherein the aqueous solution of the nitrogen-containing epihalohydrin-based resin is contacted with the anion exchange resin before, simultaneously with or after the electrodialysis treatment. the method of. 11. The method according to claim 10, wherein the anion exchange resin is a strongly basic anion exchange resin. 12. The electrodialysis device comprises at least two electrodialysis unit cells.
The method according to any one of 1 to 11. 13. The method according to claim 1, wherein the electrodialysis treatment is continuously performed. 14. A nitrogen-containing epihalohydrin-based resin having a reduced content of organic and inorganic halogens, prepared according to any one of claims 1 to 13 as an additive in the production of paper, cardboard and paperboard. Use of an aqueous solution of.